What you see in the spectrum analyzer is the DELTA of the high pass filter on the equalizer.

Unfortunately I am not an expert in psychoacoustics or logarithmics, could you explain to me why I see frequencies up to 30hz?

What a curious phenomenon.
Thank you!

 

Low pass, high pass? Which one shall it be? What's the freq and what's the slope? And up to 30Hz???

 

Maybe I explained myself badly. The eq you see behind is the filter. What you see on the analyzer is the DELTA of the filter applied to a pink noise. Why are there frequencies below 13khz?

 

That much was clear.

Still no info about freq and slope...
And maybe check the title vs your first post - contentwise?

...

Ak, ok, I think I got it. You applied an LP at 13kHz, right?
If yes, switch the filter to linear phase, listen and watch.

 

Last edited: Oct 12, 2024

Thc image shows an EQ with a Low Pass Filter at 13kHz. Thats how Low Pass filters work

If you want to cut the Lows use a High Pass filter.

 

Last edited: Oct 12, 2024

Phase shift, no?

 

Not quite. The image in the background shows the LP, the image in the foreground shows the analysis of its delta. And he wonders why there're so many low freqs left in the delta.

 

Yes, he has a low-pass filter set at 13kHz, which explains why frequencies below 13kHz are passed through—that’s how low-pass filters work.
If he didn’t want any audio below 13kHz, he should have used a low-cut (high-pass) filter, as shown in the image I posted above.

 

No, it's about the delta of the EQ, not the normal audible result.

https://www.production-expert.com/production-expert-1/how-to-use-delta-solo-in-any-daw

 

Thank you, that was what I meant, sorry if it wasn't clear

 

The 12dB/oct minimum phase LP filter introduces a tiny little bit of phase shift over the whole frequency range, so comparing it to the original signal by delta'ing, you get this misleading curve. Misleading because you might think the LP filter cuts so much lower frequencies, but they are just shifted a little bit, you won't hear that by listening to the filtered signal on it's own, just by substracting the original.

So delta'ing signals with phase shift of any kind won't get you the real audible difference, and as No Avenger already said, if you use a linear phase EQ, delta'ing would show a whole different curve.